North Korea stoked regional tensions Wednesday, threatening more nuclear tests and saying additional sanctions imposed on it would be considered an act of war, as nervous neighbors raced to bolster defenses and punish Pyongyang.

South Korea said it was making sure its troops were prepared for atomic warfare, and Japan imposed new economic sanctions to hit the economic lifeline of the communist nation’s 1 million-member military, the world’s fifth-largest.

North Korea, in its first formal statement since Monday’s claimed atomic bomb test, hailed the blast as a success and said attempts by the outside world to penalize North Korea with sanctions would be considered an act of war.

President Bush demanded stiff sanctions on North Korea Wednesday for its reported nuclear test and asserted the U.S. has “no intention of attacking” the reclusive regime despite its claims that it needs atomic weapons to guard against such a strike.

Still, in a Rose Garden news conference, Bush said the United States remains committed to diplomacy but also “reserves all options to defend our friends in the region.”

He also vowed increased military cooperation with allies, including bolstering ballistic missile defenses in the region and increased efforts to prevent Pyongyang from importing missile and nuclear technology.